Angus McKechnie (Fought in Waterloo)

I'm looking for information on a Angus McKechnie who was born in 1782 in Scotland (unconfirmed) and Died in 1862 in England.(unconfirmed). It's possible he was a Chelsea Pensioner" (unconfirmed). His wife was Belle MacIntosh (unconfirmed). It's said that he served in the British military and fought in the battle of Waterloo with Wellington in 1812 or 1815. Does anyone know such a person or know how I can locate the muster roll or list of officers who might have fought in that battle. Help! I'm stuck